Project Details
Projekt
Elastic properties of CdSe/Zns core/shell nanorods and nanowires
Applicant
Professor Dr. Christian Thomsen
Subject Area
Experimental Condensed Matter Physics
Term
from 2006 to 2010
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 26191643
The physical properties of nanowires or nanorods differ qualitatively from the corresponding bulk materials due to the reduced dimension. We plan to investigate the thermal properties of several nanostructures when illuminated and heated with visible light. The high surfaceto- volume ratio of nanostructures leads to an equilibrium temperature which is given mostly by the thermal conductivity of the surrounding gas and not by thermal conduction along the nanowire as often assumed in the literature. Si nanowires, e.g., can be used as gas-type or gaspressure sensors, since the thermal conductivity of a surrounding gas depends on its molecular weight and pressure. From the ¿ for most materials well-known ¿ temperature dependence of the phonon frequency the temperature of a nanostructure can be determined optically via Raman spectroscopy.Two limiting cases are particularly interesting: In vacuum the heat dissipation is dominated by radiation and thermal conduction along a nanowire. And secondly, when immersed in superfluid helium the thermal resistance (Kapitza resistance) at the interface of a nanostructure to liquid helium limits the cooling of the nanostructure. In nanostructures with core and shell materials ¿ a particularly important application of nanorods ¿ there is an additional interface which contributes to the thermal resistance. We plan to study the interface via the Kapitza resistance of Si-nanowires and CdSe nanorods in a region where it becomes the limiting physical effect for heat dissipation.Size quantization has an important influence on the electronic and vibrational states of a material in reduced dimension of nanowires which needs to be taken into account in the analysis. We will study with Raman scattering and luminescence the quantization in Si nanowires and CdSe nanorods. The experimental results are compared to results of molecular dynamics of the thermal properties and ab initio computations of the electronic and vibrational states.
DFG Programme
Priority Programmes
